tools: unused ports: optional address parameter

tools: unused ports: optional address parameter

While it should be impossible to bind to a wildcard address
when the port is in use by any other address there's one
case where this is allowed, and that's when the port is in
use by an ipv6 address while trying to bind to an ipv4
wildcard.
This currently happens when qemu finds ::1 for the
'localhost' we pass to qemu's spice address while we're
resolving the local nodename via IPv4.